Virtual anthropology: a preliminary test of macroscopic observation versus 3D surface scans and computed tomography (CT) scans

Virtual anthropology (VA) is based on applying anthropological methods currently used to analyse bones to 3D models of human remains. While great advances have been made in this endeavour in the past decade, several interrogations concerning how reliable these models are and what their proper use should be remain unanswered. In this research, a fundamental assumption of VA has been investigated: if the way we perceive and apply an anthropological method is truly similar when looking at bones macroscopically and through various 3D media. In order to answer, 10 skulls of known age and sex were scanned using a computed tomography (CT) scanner and a 3D surface scanner. Two observers separately applied a defined staging method to eight suture sites on these skulls, first looking at the bone macroscopically, then at the 3D surface scan, and finally on the CT scan. Two rounds of observation were carried out by each observer. Intra- and inter-observer error were evaluated, and two sample t-tests used to evaluate if the different types of medium used yielded significantly different observations. The results show a high degree of inter-observer error, and that data obtained from 3D surface scans differ from macroscopic observation (confidence level 95%, P ≤ 0.05). CT scans, in these settings, yielded results comparable to those obtained through macroscopic observations. These results offer many possibilities for future research, including indications on the kind of anthropological methods and anatomical landmarks that might be reliably transferable to the virtual environment. All current methods used in traditional anthropology should be tested, and if they prove unreliable, new techniques to analyse bones from virtual models should be developed.

Key points

• Large discrepancies between observation on dry bones and computer-generated 3D models (surface scans or CT scans) could lead to the re-evaluation of the suitability of traditional anthropological methods for application on 3D models.
• This preliminary study evaluates whether macroscopic, 3D surface scans, and CT scans viewings generate different observations.
• The results indicate that the data are not always coherent across all three media of observation.
• Explanations include the aspect given to the bone by the 3D software, differences between handling bones in real life versus on a computer, and level of expertise of the observers.

     

171例脑干颅神经损伤

目的　观察头部受力致脑干颅神经损伤的形态学改变 ,探讨脑干颅神经损伤形成机制及其与头受力部位和方式的关系。方法　 171例脑干标本 ,于双侧第 3～ 12对颅神经的根部水平横切取组织块 ,常规固定、脱水、包埋、切片、HE染色 ,光镜检查。结果　所有标本均见颅神经损伤。有动眼神经损伤 ( 12 0例 ,70 2 % ) ,面听神经损伤( 92例 ,5 3 8% ) ,三叉神经损伤 ( 85例 ,49 7% ) ,外展神经损伤 ( 4 5例 ,2 6 3 % ) ,舌下神经损伤 ( 3 1例 ,18 1% ) ,迷走神经损伤 ( 2 7例 15 8% ) ,舌咽神经损伤 ( 2 4例 ,14 0 % )及滑车神经和副神经损伤 (各 10例 ,5 8% )。损伤可为单侧或双侧 ,累及单条或多条。病理形态学改变有出血 ( 4 2例 ,2 4 6% ) ,水肿 ( 2 6例 ,15 2 % ) ,神经根部组织结构变形 ( 71例 ,41 5 % ) ,根部撕裂 ( 3 2例 ,18 7% )等。结论　脑干颅神经损伤是脑干损伤的并存病变 ;位脑干高位的颅神经损伤比位低位的多 ,粗的神经损伤比细的多而严重 ;动眼、面、听神经损伤的发生率较高。     

Measurements of the Foramen Magnum and Mandible in Relation to Sex Using CBCT

The purpose of this study was to evaluate pre‐existing CBCT images of a large sample of adult females and males to provide data on foramen magnum and mandibular measures of sexual dimorphism for use as a reference sample in cases of establishing identity in unknown fragmentary skulls. The study group consisted of 161 adult patients. 3D images of the patients were assessed retrospectively. FM measurements were obtained from reformatted axial sections. Six mandibular measurements were taken. According to the results, the study identified four mandibular measurements as final predictors of sex which are as follows: the gonial angle (G‐angle) and ramus length (Ramus‐L), gonion–gnathion length (G–G‐L) and bigonial breadth (BG‐Br). It was found that the cross‐validated grouped overall predictive accuracy was 83.2% for FM and mandible measurements. It could correctly identify males in 77.3% and females in 87.4% of the cases. To assess sexual dimorphism, the gonial angle and ramus, gonion–gnathion lengths, and bigonial breadth of the mandible and sagittal diameter of the FM may be used on CBCT images.     

Metric Sex Determination of the Human Coxal Bone on a Virtual Sample using Decision Trees

Decision trees provide an alternative to multivariate discriminant analysis, which is still the most commonly used in anthropometric studies. Our study analyzed the metric characterization of a recent virtual sample of 113 coxal bones using decision trees for sex determination. From 17 osteometric type I landmarks, a dataset was built with five classic distances traditionally reported in the literature and six new distances selected using the two-step ratio method. A ten-fold cross-validation was performed, and a decision tree was established on two subsamples (training and test sets). The decision tree established on the training set included three nodes and its application to the test set correctly classified 92% of individuals. This percentage was similar to the data of the literature. The usefulness of decision trees has been demonstrated in numerous fields. They have been already used in sex determination, body mass prediction, and ancestry estimation. This study shows another use of decision trees enabling simple and accurate sex determination.     

Sexual Dimorphism of the Fetal Ilium: A 3D Geometric Morphometric Approach with Multislice Computed Tomography

Adult sexual dimorphism is well established. However, data regarding fetuses are sparse with contradictory results. Our study aimed to look for fetal sexual dimorphism. Multislice computed tomography (MSCT) examinations and three‐dimensional (3D) reconstructions were recorded on 93 fetal iliac bones aged between 21 and 40 weeks of amenorrhea (WA). The collection was divided into two age groups, with a cutoff at 30 WA. The 3D geometric morphometric analysis was based on outline analysis. We used elliptic Fourier analysis (EFA) because of the difficulty of landmark positioning. Step‐by‐step reconstructions allowed a better comprehension of the fine shape details. Principal component analysis (PCA) and linear discriminant analysis (LDA) were performed on the two age groups. Results did not show any difference between male and female shapes, in both age groups. We demonstrate the feasibility of outline analysis for immature shapes, but sexual dimorphism has not been established in our collection.     

Ontogeny of Size and Shape Sexual Dimorphism in the Pubis: A Multislice Computed Tomography Study by Geometric Morphometry

Few studies have been conducted to determine sex differences in the immature coxal bone and the results were often contradictory. The authors studied sexual dimorphic differences of the pubis using geometric morphometric analysis of five osteometric landmarks recorded by multislice computed tomography (MSCT), based on three‐dimensional reconstructions of 188 children (95 boys, 93 girls) living in the region of Toulouse, southwestern France, ranging in age from 1 to 18 years old. They used geometric morphometric methodology first to test sexual dimorphism in size (centroid size) and shape (Procrustes residuals) and second to examine patterns of shape change with age (development) and size change with age (growth). Based on statistical significance test results, the pubic shape became sexually dimorphic at 13 years old, although visible shape differences were observed as early as 9 years old. This work showed that the trajectories of pubis shape (development) and size (growth) differed throughout ontogeny and between sexes.     

Pitfalls of Computed Tomography 3D Reconstruction Models in Cranial Nonmetric Analysis*

Many studies in the literature have highlighted the utility of virtual 3D databanks as a substitute for real skeletal collections and the important application of radiological records in personal identification. However, none have investigated the accuracy of virtual material compared to skeletal remains in nonmetric variant analysis using 3D models. The present study investigates the accuracy of 20 computed tomography (CT) 3D reconstruction models compared to the real crania, focusing on the quality of the reproduction of the real crania and the possibility to detect 29 dental/cranial morphological variations in 3D images. An interobserver analysis was performed to evaluate trait identification, number, position, and shape. Results demonstrate a false bone loss in 3D models in some cranial regions, specifically the maxillary and occipital bones in 85% and 20% of the samples. Additional analyses revealed several difficulties in the detection of cranial nonmetric traits in 3D models, resulting in incorrect identification in circa 70% of the traits. In particular, pitfalls included the detection of erroneous position, error in presence/absence rates, in number, and in shape. The lowest percentages of correct evaluations were found in traits localized in the lateral side of the cranium and for the infraorbital suture, mastoid foramen, and crenulation. The present study highlights important pitfalls in CT scan when compared with the real crania for nonmetric analysis. This may have crucial consequences in cases where 3D databanks are used as a source of reference population data for nonmetric traits and pathologies and during bone-CT comparisons for identification purposes.     

Ontogeny of Size and Shape Sexual Dimorphism in the Ilium: A Multislice Computed Tomography Study by Geometric Morphometry

We studied sexually dimorphic differences in the ilium using geometric morphometric analysis of 10 osteometric landmarks recorded by multislice computed tomography, based on three‐dimensional reconstructions of 188 children (95 boys, 93 girls) of mixed origins living in the area of Toulouse, southern France, and ranging in age from 1 to 18 years. We used geometric morphometrics methodology first to test sexual dimorphism in size (centroid size) and shape (Procrustes residuals) and second to examine patterns of shape change with age (development) and size change with age (growth). On the basis of statistical significance testing, the ilium shape became sexually dimorphic at 11 years of age, although visible shape differences were observed as early as 1 year of age. There was no statistically significant difference in size between sexes. Trajectories of shape (development) and size (growth) differed throughout ontogeny and between sexes.     

Sex estimation in a Turkish population using Purkait’s triangle: a virtual approach by 3-dimensional computed tomography (3D-CT)

Sex estimation is considered one of the first steps in the forensic identification process. Morphological and morphometrical differences between males and females have been used as means for morphoscopic and metric methods on both cranial and postcranial skeletal elements. When dry skeletal elements are not available, virtual data can be used as a substitute. The present research explores 3-dimensional (3D) scans from a Turkish population to test a sex estimation method developed by Purkait (2005).Overall, 296 individuals were used in this study (158 males and 138 females). Purkait’s triangle parameters were measured on computed tomography (CT) scans obtained from both right and left femora of each patient at the Bakirkoy Dr. Sadi Konuk Training Research Hospital (Istanbul, Turkey). Intra- and inter-observer errors were assessed for all variables through technical error of measurements analysis. Bilateral asymmetry and sex differences were evaluated using parametric and non-parametric statistical approaches. Univariate and multivariate discriminant function analyses were then conducted.Observer errors demonstrated an overall agreement within and between experts, as indicated by technical error of measurement (TEM) results. No bilateral asymmetries were reported, and all parameters demonstrated a statistically significant difference between males and females. Fourteen discriminant models were generated by applying single and combined parameters, producing a total correct sex classification ranging from 78.4% to 92.6%. In addition, over 67% of the total sample was accurately classified, with 95% or greater posterior probabilities.Our study demonstrates the feasibility of 3D sex estimation using Purkait’s triangle on a Turkish population, with accuracy rates comparable to those reported in other populations. This is the first attempt to apply this method on virtual data and although further validation and standardisation are recommended for its application on dry bone, this research constitutes a significant contribution to the development of population-specific standards when only virtual data are available.

Key points

• CT analysis using Purkait’s triangle is a suitable tool for assessment of sex in unidentified individuals.
• The best overall estimation rate was achieved with the F11 model, with around 92% of accuracy.
• The results suggested 78.4% to 92.6% correct sex identification rates.
• More research is needed to expand the sample set and verify the results.

     

Sex Classification Using the Three‐Dimensional Tibia Form or Shape Including Population Specificity Approach

The aims of this study were to enable geometric morphometric sex classification using tibial proximal and distal sexual dimorphism and to evaluate the secular trend of tibial shape/form from the early 20th century to the present day. The study samples consisted of 61 adult tibias from an early 20th‐century Czech population and 57 three‐dimensional tibias from a 21st‐century population. Discriminant function analysis with cross‐validation was carried out to assess the accuracy of sex classification. Shape analysis revealed significant sex differences in both tibial extremities of the 21st‐century sample and in the proximal tibia of the 20th‐century population. Sex‐based divergence varied between the analyzed samples, raising the issues of population specificity and diachronic change. Classification using tibial form was more successful than using tibial shape. The highest values of correct assignment (91.80% and 88.52%) were found using the form from the early 20th Czech population.     

Human coxal bone sexual dimorphism and multislice computed tomography: geometric morphometric analysis of 65 adults

The authors studied sexually dimorphic differences in coxal shape using geometric morphometric analysis of 15 osteometric landmarks recorded by multislice computed tomography (MSCT), based on three-dimensional reconstructions of 65 Caucasian adults. Geometric morphometric analysis, principal component analysis, canonical variates analysis, and other discriminant analysis (Goodall's F-test and Mahalanobis distance) were performed for the three separate bones of the left innominate (pubis, ilium, and ischium), the modified pubis (pubis and ischiopubic ramus), the modified ilium (ilium and ischial spine), three bone complexes (ischiopubic, iliopubic, and ilio-ischial), and the complete innominate. A cross-validation test was also performed. All areas studied were dimorphic, but results for sexual dimorphism in decreasing order were as follows: the modified pubis, followed by the ischiopubic complex, the iliopubic complex and the complete innominate, the pubis, the modified ilium, the ilio-ischial complex, the ilium, and finally the ischium. These results show the potential of this approach for future anthropological research.     

Postmortem chest computed tomography for the diagnosis of drowning:a feasibility study

It may be difficult to distinguish the cause of death in drowning cases without specific findings. The aim of this study was to explore the forensic value of thoracic postmortem computed tomography (PMCT) using routine images and three-dimensional (3D) image reconstructions. The imaging data of PMCT examinations of six drowning cadavers, aged 21–54 years, were analyzed. Twelve victims of sudden death from coronary artery disease (CAD) were chosen as a control group. After 3D bilateral lung images were reconstructed using image processing software, an interactive medical image control system was used to measure and analyze parameters including lung volume, lung volume ratio, mean CT value of the whole lung, and lung CT value distribution curves. Lung volume and lung volume ratio were used to assess the shape changes of the lung. Lung CT value distribution curves showed the corresponding number of pixels of the different CT values in the lung image. Lung volume was not significantly larger in drowning cases (mean 2 958 cm³) than in controls (mean 2 342 cm³). Lung volume ratio values in the drowning group (mean 0.3156) were greater than those in the control group (mean 0.2763); (P = 0.02). There was no significant difference between the drowning and control group in the mean CT value of the whole lung. There were differences between lung CT value distribution curves in drowning victims and controls, with drowning victims showing a single peak and CAD cases showing a bimodal distribution. Thoracic PMCT is helpful for the forensic medical diagnosis of drowning. Lung volume ratio and lung CT value distribution are potential indicators to distinguish between drowning and CAD.     

PMCT在机械性窒息方面的研究进展

机械性窒息是公安法医日常检案中最常见的死因之一.如何快速准确的判断死者是否为机械性窒息死亡、以及作案手段是判断案件性质、指引案件侦破方向的重要因素.在法医鉴定过程中,诊断机械性窒息需要结合尸体体表征象、尸体内部征象、组织病理学检验等多方面综合判断.PMCT在骨折的检测、异物的检测和气体的检测方面具有极大的优势,在许多国...     

A Validation Study of the Langley et al. (2017) Decision Tree Model for Sex Estimation

Langley et al. (2017) developed a sex estimation decision tree utilizing two traditional cranial traits (glabella and mastoid) and a new trait: zygomatic extension. This study aimed to test the reliability of their zygomatic extension scoring method and validate their sex estimation method. Ordinal score data were collected from 281 male and female U.S. White and Black individuals. The five traditional cranial traits were collected from physical specimens, while zygomatic extension was scored from 3D cranial models. Intra‐ and interobserver analyses carried out on a subsample of 30 individuals indicate good agreement between zygomatic scores. The decision tree correctly sexed 71.5% of the sample, but a strong sex bias (94.2% correct for females, 49.3% correct for males) severely limits the utility of this method. The Walker (2008) and Stevenson et al. (2009) methods produced higher accuracy rates (80.8% and 82.6%, respectively), although these methods also produced sex and ancestry biases.     

死后尸体CT在法医学鉴定中的应用价值初探

目的 对不同类型案件中的死者进行死后尸体CT扫描和常规尸体解剖,探索PMCT在法医学鉴定中的应用价值.方法 对7例因不同原因死亡的个体进行全身PMCT扫描,随后进行系统的尸体解剖,通过比较两种方法检测的结果,分析PMCT与传统尸体解剖在不同类型案件中应用的优点和不足.结果 在7个案例中,尸体上总共检出67处阳性发现.其...     

Fingerprint analysis for the determination of hand origin (right/left) using the axis slant in whorl patterns

Fingerprints are frequently encountered during both civil and criminal investigations. Fingerprints possess numerous characteristics that assist with personal identification. Determining the hand of origin (right or left) for an individual fingerprint would help reduce investigation time and potentially eliminate certain suspects. In this study, we collected a total of 2 900 single digit fingerprints from 290 individuals, and the whorl axis slant was examined in the 743 whorl pattern fingerprints (385 from the right hand and 358 from the left hand). A slant towards the right side was present in 81.82% of samples from the right hand, while a slant towards the left side was observed in 80.73% of samples from the left hand. After applying a chi-square test to the dataset, the results were found to be statistically significant for the determination of hand origin. Our results suggest that the whorl axis slant in a fingerprint is indicative of hand origin (right or left).

Key points

• Single digit fingerprints with whorl pattern were analyzed.
• Whorl “axis slant” was used to determine the hand origin.
• Right axis slant would indicate the right hand of the print.
• Left axis slant would indicate the left hand of the print.

     

A comparison between neural network and other metric methods to determine sex from the upper femur in a modern French population

Forensic anthropologists are frequently asked to assess partial or badly damaged skeletal remains.One such request led us to compare the predictive accuracy of different mathematical methods using four non-standard measurements of the proximal femur (trochanter–diaphysis distance (TD), greater–lesser trochanter distance (TT), greater trochanter width (TW) and trochanter–head distance (TH)). These measurements were taken on 76 femurs (38 males and 38 females) of French individuals. Intra- and inter-observer trials did not reveal any significant statistical differences. The predictive accuracy of three models built using linear and non-linear modelling techniques was compared: discriminant analysis, logistic regression and neural network. The neural network outperformed discriminant analysis and, to a lesser extent, logistic regression. Indeed, the best results were obtained with a neural network that correctly classified 93.4% of femurs, with similar results in males (92.1%) and females (94.7%). Univariate functions were less accurate (68–88%). Discriminant analysis and logistic regression, both using all four variables, led to slightly better results (88.2% and 89.5%, respectively). In addition, all the models, save the neural network, led to unbalanced results between males and females. In conclusion, the artificial neural network is a powerful classification technique that may improve the accuracy rate of sex determination models for skeletal remains.     

Determination of barbiturates in hair samples by using a validated UHPLC-HRMS method: application in investigation of drug-facilitated sexual assault

In recent years,benzodiazepines and benzodiazepine-like drugs are the most common substances associated with drug-facilitated sexual assaults(DFSA);however,barbiturates are also detected occasionally.Segmental hair analysis provides useful information on the historic pattern of drug use,enabling differentiation between single exposure in DFSA cases and chronic use.However,sensitive and specific methods for barbiturate analysis in hair samples are needed.Herein,we present an ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry(UHPLC-HRMS)method for qualitative and quantitative determination of seven barbiturates in hair samples.Firstly,a hair strand was decontaminated and then freeze-milled in liquid nitrogen.Next,50mg of powdered hair was extracted with methanol in an ultrasonic bath for 10 min in the presence of 10 ng phenobarbital-d5.The supernatant was dried under nitrogen gas,and the pellet was dissolved in 100 μL mobile phase.Afterwards,10 μL of the suspension was injected into the UHPLC-HRMS system.The present method involved two UHPLC conditions for determination of barbiturates(I)and identification of the structural isomers amobarbital and pentobarbital(II).This method showed satisfactory linearity in a range of 0.02–20.00 ng/mg for UHPLC conditions I and II,both with a high determination coefficient(0.9991–0.9999).The selectivity,intra-and interday precision,accuracy and matrix effect of the method were acceptable.Next,the validated method was applied to investigate an authentic DFSA case.Hair samples(black,approximate 25cm long)were collected 3 months after the assault,and the proximal segments(0–5 cm from the root;each segment was 1 cm long)were analysed.Amobarbital was detected at a concentration of相似文献   

122例鼻部骨折X线和CT诊断的法医学分析

目的　探讨CT在鼻部骨折诊断中的优点。方法　观察 12 2例鼻损伤伤者的鼻部CT和普通X线片 ,对鼻部诸骨骨折进行对比分析。结果　 12 2例鼻部骨折 (鼻骨骨折 3 2例 ,上颌骨额突骨折 3 3例 ,鼻中隔骨折 9例 ,多发性骨折 48例 )均经CT认定。其中 40例因X线片漏诊直接通过高分辨率鼻骨CT薄层扫描认定 ;82例通过鼻骨侧位X线片显示有鼻部骨折 ,因存在骨折类型认定不准确和 /或有漏诊鼻部其它部位骨折可能 ,通过鼻骨CT认定。结论　鼻骨侧位X线片易漏诊、误诊鼻部骨折 ;鼻骨CT能避免鼻部诸骨骨折的漏诊及误诊 ,且骨折认定准确。